Question

[RickB]

On the live plug, the scenario I had in mind is gen running and shore power NOT plugged in. If you turned both breakers on, the prongs at the shore power inlet would be live and dangerous. And if you connected your power cord to that inlet, then the shore-end of the cord would now have live pins exposed.

That is the reason there is an interlock. Unless the boat is equipped to allow paralleling of power sources there must be a mechanical interlock to prevent both sources from being connected to the buss at the same time. The OP asked why there is an interlock, that is the reason.

If you are interested in electrical safety then you must consider the sequence of events when switching between shore power and generator power and follow them. There should be no means (interlock) or reason (forgetting to do something) that will create a hazardous condition. If the exposed prongs are energized, either the boat is not properly equipped or the use is not adequately prepared to handle that procedure.

Why would anyone handle an energized shore power cord in any event? The boat end and shore end breakers should be open until the boat (and the user) are prepared to receive shore power. The shore end breaker should be closed first so that the supply can be verified at the switchboard and only then should the shore power breaker on the boat be closed. That procedure provides several opportunities to confirm that all is in order and avoids handling any energized components.

Guns and cars can be dangerous to those who don't know how to operate them, boats can be dangerous as well, electricity is no different, we are not talking about unknown territory and we are not talking about building codes or house wiring rules.

 

[Delfin]

But I can't resist...I love the one where if you touch the prongs of a 110 shore power cord you will DIE......man...I giggled myself to sleep last night...

Just to clarify your point... Based on your referenced lifetime of experience, if I jumper my Shore/Generator rotary switch to combine these circuits, start my 20kw genset and plug in the 240 v 50 amp shore power cord, then grab a hold of the male end, (now energized), the idea that I might die by making contact with 80 amps at 240 volts on a metal boat in sea water is so remote that we should deride someone who suggests it?

This is why sites like this can be so depressing.

 

[rwidman]

................ Why would anyone handle an energized shore power cord in any event? ...........

Simple. Because he or she doesn't know any better or doesn't know the cord is energized. It could be your wife, your children or grandchildren, a marina employee or a slip neighbor trying to help.

Why do lawnmowers have to shut down the engine or blades if the handle interlock is releasd? Why would anyone stick their hand under a running lawnmower? Apparently, some people have done just that, that is why they now have the safety interlock.

 

[RickB]

... if I jumper my Shore/Generator rotary switch to combine these circuits, start my 20kw genset and plug in the 240 v 50 amp shore power cord, then grab a hold of the male end, (now energized)...

You would be a strong candidate for the Darwin Award.

We can install interlocks to help prevent mistakes and institute procedures to promote safe operating practices, but nothing can prevent stupid. Sometimes the herd is culled for good reason.

 

[psneeld]

Rick, I would really like to stop arguing with you and your buddy on every little issue so if you two will agree to stop with the insulting language, we could all have a more enjoyable time on this forum and perhaps we could all learn from each other.

Believe me it's not us!!!!

 

[psneeld]

Just to clarify your point... Based on your referenced lifetime of experience, if I jumper my Shore/Generator rotary switch to combine these circuits, start my 20kw genset and plug in the 240 v 50 amp shore power cord, then grab a hold of the male end, (now energized), the idea that I might die by making contact with 80 amps at 240 volts on a metal boat in sea water is so remote that we should deride someone who suggests it?

This is why sites like this can be so depressing.

Wouldn't say you were incorrect...but RIGHT IN MY POST...I said 110...and sure you can kill yourself with 110 or 220...but...

The probabilities are pretty low unless a lot of "correct" happens. Most people I know have been "bit" at least a few times with nothing more than a good tingle.

Of course they are depressing if you take them or yourself too seriously...

 

[Pineapple Girl]

Very interesting conversation. Enlightening to read about different technologies on different types of boats and what great commercial technology is trickling down for use on our toys.

As far as taking Internet advice for gospel and applying it in practice-we got a LOT of advice about how to install our inverter and new house bank. Read Nigel Calders book. Mulled it over for months. And paid a marine electrician to do it. Despite so many people telling us we could go it ourselves. Just not worth it to us to mess with something we really didn't understand.

 

[RT Firefly]

Greetings,
"Just not worth it to us to mess with something we really didn't understand." I use the same approach with women.

 

[twistedtree]

OMG, time to pull the eject lever. I'm outa this "conversation".

 

[psneeld]

Greetings,
"Just not worth it to us to mess with something we really didn't understand." I use the same approach with women.

That's why you are a hall of famer....you appreciate humor and it's necessity...

especilly the taking yourself so seriously part...

 

[Codger2]

Just not worth it to us to mess with something we really didn't understand.

That's certainly been my approach over the years. I admit, however, that a lot of people don't have the "where with all" (finances) to hire the work out and that's where the danger lies. Many DIYfers take bad advice from this forum (and I've read a lot of it!) and get themselves and their boat in one hell of a mess.

 

[Delfin]

Wouldn't say you were incorrect...but RIGHT IN MY POST...I said 110...and sure you can kill yourself with 110 or 220...but...

The probabilities are pretty low unless a lot of "correct" happens. Most people I know have been "bit" at least a few times with nothing more than a good tingle.

Of course they are depressing if you take them or yourself too seriously...

The OP asked why interlocks. TT explained why, with one of the reasons being that without interlocks one can easily imagine a situation on a boat where one might die without interlocks.

With all your experience, I should think you would be aware that voltage is not what kills you, but amperage. Since 30 mA is considered sufficient to kill someone, it's not too hard to imagine that 80 amps would also do the trick, whatever the voltage.

My point is not, of course that anyone is likely to be dumb enough to remove the physical protections built into every sane installation to prevent accidental electrocution. Rather it is that the kind of gratuitous insults dished out by posers whose self esteem seems somehow to be linked to trashing others diminishes the usefulness and pleasure of participating on this site.

So, I gather we're agreed that interlocks are there to prevent possible problems, one of which could be electrocution however remote the possibility, as TT noted?

 

[bobofthenorth]

Not naming any names but on forums in general conflict generally arises when a few posters feel compelled to demonstrate their vastly superior knowledge, regardless of the topic at hand. I subscribe to the notion that explanations need to be targetted to the audience. I'm sure there are systems on the space shuttle that would be really keen to have on Gray Hawk but I'm just as likely to have access to them as I am to install generators that are capable of paralleling shore power.

Neither NEC nor ABYC have any legal status aboard my boat but common sense dictates that I should at least understand the principle safeguards built into both codes if I am going to tackle onboard wiring. In both cases many of the provisions are in the code because somebody died. That doesn't mean that violation of that provision will automatically result in death but for many of the provisions at some time somebody died and the clause was subsequently created. In that context I wouldn't be too quick to ridicule either code.

 

[psneeld]

The OP asked why interlocks. TT explained why, with one of the reasons being that without interlocks one can easily imagine a situation on a boat where one might die without interlocks.

With all your experience, I should think you would be aware that voltage is not what kills you, but amperage. Since 30 mA is considered sufficient to kill someone, it's not too hard to imagine that 80 amps would also do the trick, whatever the voltage.

My point is not, of course that anyone is likely to be dumb enough to remove the physical protections built into every sane installation to prevent accidental electrocution. Rather it is that the kind of gratuitous insults dished out by posers whose self esteem seems somehow to be linked to trashing others diminishes the usefulness and pleasure of participating on this site.

So, I gather we're agreed that interlocks are there to prevent possible problems, one of which could be electrocution however remote the possibility, as TT noted?

Absolutely...the guys who are the problem aren't even the ones who thought you couldn't parralel the genset and shore power...which you can and links provided for the stubborn...but refused to let just that tiny little portion go by the wayside. The problem is that they don't even know they are "it".

Both Rick and I acknowledged that interlocks are needed or useful to the small boater because both the size of our boats the systems we employ our budgets and out typical operatonfg proceedures.

He only mentioned that paralleling shore/genset was possible and knowing he was correct chimed in because the same guys also refuse to acknoledge experience in the field.

So most of this thrread is easy to see for the informed once you sort through the rest of the crap.......which you have seemed to have done...

 

[psneeld]

Not naming any names but on forums in general conflict generally arises when a few posters feel compelled to demonstrate their vastly superior knowledge, regardless of the topic at hand. I subscribe to the notion that explanations need to be targetted to the audience. I'm sure there are systems on the space shuttle that would be really keen to have on Gray Hawk but I'm just as likely to have access to them as I am to install generators that are capable of paralleling shore power.

Neither NEC nor ABYC have any legal status aboard my boat but common sense dictates that I should at least understand the principle safeguards built into both codes if I am going to tackle onboard wiring. In both cases many of the provisions are in the code because somebody died. That doesn't mean that violation of that provision will automatically result in death but for many of the provisions at some time somebody died and the clause was subsequently created. In that context I wouldn't be too quick to ridicule either code.

Not really...the problem is when the uninformed or not as experience keep it up after a simple explanation is posted by those in the know . Even when reasonable, reputable links are provided.

They continue...with no further investigation or proof reading on their part keep it up...then even when the truth comes out or they realize they weren't even discussing the same thing...keep it up...

For them there probably is no hope and they are part of the forum no matter what..just like the guys with vastly superior knowledge.

And I'll be the first to proclaim there's lots that I don't know...but being a marine pro for a long time..I do know some...and the real beauty is....if you stay long enough...there's always a topic where anybody is king!!

Better to have a few really experienced people than everyone groping around in the dark...and again...I'm not one of those unless you are talking small boat handling, rescue or survival...

 

[RickB]

...the problem is when the uninformed or not as experience keep it up after a simple explanation is posted by those in the know . Even when reasonable, reputable links are provided.

They continue...with no further investigation or proof reading on their part keep it up...then even when the truth comes out or they realize they weren't even discussing the same thing...keep it up...

For them there probably is no hope and they are part of the forum no matter what..just like the guys with vastly superior knowledge.

That is an excellent appraisal. The uninformed tend to make sweeping statements and promote ideas and conclusions to support them. They sometimes follow that with advice that is often dangerous to the body and the bank account. They are usually the first to respond and generally miss the point far enough to merely confuse the issue.

When corrected they tend to react and lash back in order to preserve what they believe is their own and only true version of what little they know. And some times what some people see as an insult is merely an objective appraisal or just an observation.

 

[IslandEagle]

Wouldn't say you were incorrect...but RIGHT IN MY POST...I said 110...and sure you can kill yourself with 110 or 220...but...

The probabilities are pretty low unless a lot of "correct" happens. Most people I know have been "bit" at least a few times with nothing more than a good tingle.

Of course they are depressing if you take them or yourself too seriously...

As I mentioned, try Googling "dock electrocution kids" and have aread. The problem is that it might not be you who gets killed.